This patent document is directed to a freezer, in particular ultra-low temperature freezer, comprising an interior and a housing surrounding the interior and having an outer door, wherein the interior comprises several cooling compartments in a stacked arrangement and wherein each cooling compartment has an inner door.
Freezers and ultra-low temperature freezers are known in the prior art and are used, for example, in chemical, biological, biochemical, medical or forensic laboratories for storing laboratory samples, in particular solid, gel-like or liquid samples, at low temperatures, in particular ultra-low temperatures. Low temperatures are considered to range between 0° C. and −50° C., while ultra-low temperatures are considered to range between −50° C. and −90° C. Under such conditions, laboratory samples based on an aqueous solution and many other liquid, gel-like or solid samples will freeze.
Freezers are typically upright freezers, which are placed on the floor or under bench. The freezers have an interior or inner volume for storing the samples, and a housing is provided surrounding or encasing the interior or inner volume. The housing includes an outer door or access door, which is often a front door hinged to a side edge of the housing. The housing of the freezer is typically configured to thermally insulate or isolate the interior of the freezer from the surrounding atmosphere, in particular to provide a thermal isolation for providing (ultra-) low temperatures within the interior. Typically, a freezer is substantially in the form of a cuboid and also has a substantially cuboid-shaped interior, which is limited by the housing of the freezer.
The cooling of the interior of the freezer usually is achieved by the provision of an (ultra-) low temperature refrigeration unit. The cooling of a freezer, for example, can be achieved by cooled inner walls, which contact the interior. The cooling may be achieved by conduction of heat from the air inside the inner volume to the cooled inner walls, which is supported by the convection of the air. Evaporation or cooling tubes of a refrigeration system can be provided to cool the walls, which can be connected to an (ultra-) low temperature refrigeration unit, which may be arranged, for example, below the interior of the freezer.
To provide for optimized storing conditions, a substantially uniform temperature distribution within the freezer is preferred. For example, large temperature differences between different cooling compartments may lead to differences in the storing conditions in these compartments and may have a negative influence on the samples stored therein.
It is therefore an object to provide a freezer, in particular an ultra-low temperature freezer, with an improved temperature distribution, in particular an improved temperature uniformity within the freezer interior.